As alloys representing a shape memory effect, Au—Cd, Ti—Ni, Cu—Al—Ni, Ag—Cd, Fe—Pt, Cu-Zu, Cu—Au—Zn, and the like had been reported. In practical terms, a Ti—Ni-based alloy having excellent shape memory effect stability and mechinability had been known as the dominant alloy.
However, the shape memory alloy of Ti—Ni binary system has a transformation temperature in a range of 330 to 220 K, and is not yet employed to parts of high-temperature home appliances, automobiles, aircrafts, high-temperature actuators, and the like which are exposed to a temperature larger than the transformation temperature. To overcome this, researches for the development of high-temperature shape memory alloys were conducted. Specifically, it had been known that the transformation temperature is increased when elements such as Pd, Pt, Au, or Hf are added to the Ni—Ti binary alloy.
However, since the elements such as Pd, Pt, Au, or Hf are very expensive, it was difficult to practice the high-temperature shape memory alloy using the elements.